As more antibiotics have been prescribed or used at an ever increasing rate for a variety of illnesses, increasing numbers of bacteria have developed a resistance to antibiotics. Larger doses of stronger antibiotics are now being used to treat ever more resistant strains of bacteria. Multiple antibiotic resistant bacteria have consequently developed. The use of more antibiotics and the number of bacteria showing resistance has led to increasing the amount of time that the antibiotics need to be used. Broad, non-specific antibiotics, some of which have detrimental effects on the patient, are now being used more frequently. Also, antibiotics do not easily penetrate mucus linings. Additionally, the number of people allergic to antibiotics appears to be increasing. Consequently, other efforts have been sought to first identify and then kill bacteria.
The upper respiratory mucosa can serve as a reservoir for Streptococcus pneumoniae. Through the use of phage lytic enzymes, nasopharyngeal colonization by S. pneumoniae provides promising new approaches to reducing S. pneumoniae infection and carriage. Nasopharyngeal carriage is a major reservoir for Streptococcus pneumoniae in the community and a potential source of infection and infectious communication by these bacteria.
While eliminating reservoirs of S. pneumonia in humans and animals would reduce incidence of related infections, no intervention other than antibiotics has been available for this purpose. Streptococcus pneumoniae remains a significant human pathogen because of the morbidity and mortality it causes in young children, the elderly and in immunocompromised patients. S. pneumoniae is found in the nasopharynx of 11-76% of the population, averaging 40-50% for children and 20-30% for adults (F. Ghaffar, I. R. Friedland, G. H. McCracken, Jr., Pediatr Infect Dis J 18, 638-46. (1999), incorporated by reference). The asymptomatic carrier state, particularly in children, is thought to be the major reservoir of the pathogen, which is transmitted by salivary aerosols and direct contact. Under predisposing conditions, such as a concomitant viral infection, the organism will spread locally or systemically.
Pneumococci account for the majority of cases of acute otitis media (AOM), community acquired pneumoniae and bacterial meningitis, and can cause lethal sepsis. In recent years, resistance of Pneumococci to multiple antibiotics has increased worldwide. Many studies have shown that treatment with antibiotics in children, be it for AOM or eradication of group A streptococci, even with a single dose, is associated with an increase in the carriage of resistant pneumococcal strains (E. Melander, et al., Eur J Clin Microbiol Infect Dis 17, 834-8. (1998), T. Heikkinen, et al., Acta Paediatr 89, 1316-21. (2000), and J. Y. Morita, et al., Pediatr Infect Dis J 19, 41-6. (2000), all incorporated by reference). Treatment of pneumococcal disease is thus becoming more difficult than in the past. The number of annual cases of AOM in the United States is about 7 million, while invasive pneumococcal infection was recently estimated to be more than 60,000 with an overall mortality of 10%. Although most of these latter cases occurred in persons eligible for vaccination (K. A. Robinson, et al., JAMA 285, 1729-35. (2001), incorporated by reference.), vaccination rates remain insufficient (C. G. Stevenson, M. A. McArthur, M. Naus, E. Abraham, A. J. McGeer, CMAJ 164, 1413-9. (2001), S. Gleich, et al., Infect Control Hosp Epidemiol 21, 711-7. (2000) incorporated by reference). Furthermore, despite the progress that has been made with the development of conjugate vaccines for children younger than 2 years, it remains doubtful that vaccination alone is sufficient to eliminate carriage of and disease caused by Pneumococci. The new conjugate vaccines include a restricted number of pneumococcal serotypes and protect only incompletely against colonization with these. About one third to one half of cases of AOM are caused by strains not included in a 9-valent vaccine (S. I. Pelton, Vaccine 19 Suppl 1, S96-9. (2000), incorporated by reference). Moreover, an increase in the carriage of non-vaccine serotypes has been reported (N. Mbelle, et al., J Infect Dis 180, 1171-6. (1999), incorporated by reference). Because of these problems, there is a need for an alternative preventive strategy for situations where vaccination is insufficient, impossible or inefficient.
Eradication or even reduction of nasopharyngeal carriage is likely to reduce the transmission of S. pneumoniae and the incidence of infection. Antibiotic prophylaxis in controlled surroundings has shown limited success but carriers the risk of selective pressure resulting in an increase of resistant strains (S. D. Putnam, G. C. Gray, D. J. Biedenbach, R. N. Jones, Clin Microbiol Infect 6, 2-8. (2000). incorporated by reference). Until now, there has been no substance that can specifically reduce the number of Pneumococci carried on human mucous membranes without affecting the normal indigenous mucosal flora.
Attempts have been made to treat bacterial diseases with the use of bacteriophages. The direct introduction of bacteriophages into an animal to prevent or fight diseases has certain drawbacks. Specifically, the bacteria must be in the right growth phase for the phage to attach. Both the bacteria and the phage have to be in the correct and synchronized growth cycles. Additionally, there must be the right number of phages to attach to the bacteria; if there are too many or too few phages, there will be either no attachment or no production of the lysing enzyme. The phage must also be active enough. The phages are also inhibited by many things including bacterial debris from the organism it is going to attack. Further complicating the direct use of a bacteriophage to treat bacterial infections is the possibility of immunological reactions, rendering the phage non-functional.
Methods for obtaining and purifying bacteriophage lytic enzymes produced by bacteria infected with bacteriophage are known in the art. Recent evidence suggests that the phage enzyme that lyses the streptococcus organism may in limited cases actually be a bacterial enzyme that is used to construct the bacterial cell wall. While replicating in the bacterium, a phage gene product may cause the upregulation or derepression of a bacterial enzyme for the purpose of releasing the bacteriophage. These bacterial enzymes may be tightly regulated by the bacterial cell and used by the bacteria for the construction and assembly of the cell wall. In general, however, phage lytic enzymes are coded for by the phage genome and produced by the phage in the infected bacterial host for phage release.
Consequently, others have explored the use of other safer and more effective means to treat and prevent bacterial infections using bacteriophage lytic enzymes. For example, U.S. Pat. No. 5,604,109 (Fischetti et al.) relates to the rapid detection of Group A streptococci in clinical specimens, through the enzymatic digestion by a semi-purified Group C streptococcal phage associated lysin enzyme. This enzyme work became the basis of additional research, leading to methods of treating diseases. U.S. Pat. No. 5,985,271 (Fischetti and Loomis), U.S. Pat. No. 6,017,528 (Fischetti and Loomis) and U.S. Pat. No. 6,056,955 (Fischetti and Loomis) disclose the use of a lysin enzyme produced by group C streptococcal bacteria infected with a C1 bacteriophage. U.S. Pat. No. 6,056,954 (Fischetti and Loomis) discloses a method for the prophylactic and therapeutic treatment of bacterial infections with an effective amount of a lytic enzyme composition specific for the infecting bacteria, wherein the lytic enzyme is in an environment having a pH which allows for activity of said lytic enzyme; and a carrier for delivering said lytic enzyme. U.S. Pat. No. 6,238,661 (Fischetti and Loomis) discloses a method for the prophylactic and therapeutic treatment of bacterial infections in general, which comprise administering to an individual an effective amount of a composition comprising an effective amount of lytic enzyme and a carrier for delivering the lytic enzyme and the method of treating illnesses in general.
Bacteriophage lytic enzymes can also be used to treat various types of infected subjects through various routes of administration. For example, U.S. Pat. No. 6,248,324 (Fischetti and Loomis) discloses a composition for dermatological infections by the use of a lytic enzyme in a carrier suitable for topical application to dermal tissues. The method for the treatment of dermatological infections comprises administering a composition comprising an effective amount of a therapeutic agent, with the therapeutic agent comprising a lytic enzyme produced by infecting a bacteria with phage specific for that bacteria. U.S. Pat. No. 6,254,866 (Fischetti and Loomis) discloses a method for treatment of bacterial infections of the digestive tract which comprises administering a lytic enzyme specific for the infecting bacteria. The lytic enzyme is preferably in a carrier for delivering the lytic enzyme. The bacteria to be treated is selected from the group consisting of Listeria, Salmonella, E. coli, Campylobacter, and combinations thereof. The carrier for delivering at least one lytic enzyme to the digestive tract is selected from the group consisting of suppository enemas, syrups, or enteric coated pills. U.S. Pat. No. 6,264,945 (Fischetti and Loomis) discloses a method and composition for the treatment of bacterial infections by the parenteral introduction of at least one lytic enzyme produced by a bacteria infected with a bacteriophage specific for that bacteria and an appropriate carrier for delivering the lytic enzyme into a patient. The injection can be done intramuscularly, subcutaneously, or intravenously.